This doctoral thesis is based on the ethnography of a state secondary school situated in an average-sized town in Catalonia with a medium-low socio-economic level and a population that includes considerable numbers of immigrants both from other parts of Spain and from some African coutnries (principally Morocco and Gambia). The thesis includes bibliographical research and a theoretical clarification to situate the phenomena of indentity, racism and violence within the historical and social context of the present day. The growing importance of these phenomena and the relationships established between them are explained in this context. The first part of the thesis endeavours to provide a theoretical context for the ethnographic research and to situate the classroom observations within a much wider social framework. The second part of the thesis introduces contributions from educational sociologists and anthropologists to the analysis of how ethnic diversity, racism and violence are dealt with in schools. The third part develops the ethnographic research by focusing on the interethnic relations among the students.